Duplex telegraph



- (No-Model.)

.J. G. WILSON.

-Duplex Telegraph. No. 240,349. Patented April 19,1881.

A 0/ R illlil B B. nl'bi l'l l l'l' OOOOO WiTNE.E5E E INVN-Tfi N4 PETERS. PHoTmuTnQGRAPnfiR. WASHXNGTON o c NITE STATES PATENT OFFICE.

JOHN G. NVILSON, OF BOSTON, 'MASSAOHUSETTS.

DUPLEX TELEGRAPH.

SPECIFICATION forming'part of Letters Patent N 0. 240,349, dated April 19, 1881,

Application filed'January 5, 1881. (No model.)

To all whom it may concern Be it known that 1, JOHN CORNELIUS WIL- SON, of Boston, Suffolk county, State of Massachusetts, have invented an Improvement in Duplex Telegraphy, of which the following description, in connection with the accompanying drawing, is a specification.

My invention relates to a duplex or double transmission-telegraph in which independent messages may be simultaneously transmitted in opposite directions from one terminal station-to the other by a single wire. telegraph system it is necessary that the receiving-instrument or relay at one terminal station should be insensible to pulsations sent from that station, but capable of responding to pulsations coming from the other terminal station. This has been, in some instances, accomplished hitherto by means of neutralizingbatteries used in connection with relays of peculiar construction, the current of the said neutralizing-batteries being passed through a coil of the home relay at the same time with that of the main battery when put to line to cause a signal to be given by a distant relay, the neutralizing-battery being so arranged as to exactly oppose and annul the effect of the main battery upon the home relay without affooting the said main battery in its action on the distant relay. The normal condition of a relay in such systems, under the influence of the transmitting apparatus at the same station therewith, is demagnatized, as there is either no current at all, both batteries being ofl', or there is no effective current, both batteries being on, equal in efl'ect and opposite in action to one another. The relay is thus always ready to respond to the current from the distant station, the said current either acting alone or in addition to the two equal and opposite effects of the two home currents, and in either case having its full effect.

Various other methods of rendering a relay insensible to pulsations that are intended to afiect only another instrument have been employed; but these need no detailed description here, as they have no similarity to my invention, in which, instead of throwinga local neutralizing current upon the home relay at the same time that the main current is passed therethrough to eifect the distant relay, I

In such amaintain the condition of the home relay uniform while the home battery is being removed and thrown on for the purpose of signaling the distant station, by bringing in a current from a local battery when that of the main battery is removed, the said local current being equivalent to the main current in its effect on the home relay, but having substantially no effect at all on the distant relay. By this arrangement the normal condition of the home relay is magnetized either by the action of the main or the local battery, and it is operated to give a signal by the additional effect of the distant battery when thrown on, the said battery, if placed with its poles to actin conjunction with the home battery, giving an additional magnetic impulse to overcome the retractingspring, too strong for the main or local current alone, and give the closed signal, or, preferably, being placed to oppose the main and local batteries, neutralizing -their effect, and cause the open signal to be given when thrown on by the operator at adistant station. By this arrangement I am enabled to use a relay of the construction commonly used for ordinary single-transmission telegraph-lines, the local neutralizing current passing through the same coil as the main current.

The instruments, batteries, and connections are similarly arranged at the two terminal stations, and consequently need be described for only one station, which may, for convenience, be called the home station, the other, when referred to, being called the distant station. At both stations I place main batteries in the main-line circuit, preferably with like poles to line, and an auxiliary battery in a local circuit, the main and local circuits preferably passing through the coils of an ordinary relay common to both the currents of both batteries passing in the same direction, and by a rheostat I properly adjust the resistance of the local circuit of the auxiliary battery to make its effect on the said relay equal to that of the main battery. The coils of the relay thus form a portion of both the main and local circuits; but, if desired, the local circuit might have an independent coil in the relay, as in the existing duplex systems, thedifferenee being that in my system, the two currents are equal'and similar in effect, and one is always on'while the other is off, while in the existing systems the currents are equal and opposite in effect, and both are on or off at the same time.

In order to maintain the condition of the home relay uniform during the manipulation of the key at the home station, I employ a suitable key or transmitter having two sets of closing points operated simultaneously, one of these sets operating to remove the main battery and connect the terminal of the-main line to the ground at the same moment that the other set closes the circuit of the local battery, threby substituting its effect upon the home relay for that of the main battery removed, while by the opposite movement of the key or transmitter the local circuit is broken and the main battery put to line, thus removing the effect of the local battery from the home relay at the same instant that that of the main battery is brought into action. The local circuit, when closed, forms a branch of the main circuit, and the current is divided; but one branch contains only the resistance of the borne relay, while the other contains the whole line and distant relay, so that substantially the whole of the local-battery current passes through the home relay, and substantially none of it reach es the distant relay, and, consequently, when the main battery is removed from the line its effect upon the home relay is replaced by that of the local battery; but its effect upon the distant relay is not so replaced, and the said relay is consequently affected to give a signal when the main-battery current at the home station is passing throughthe coils of the home relay, which is the normal condition.

\Vhile no message is being sent from the home station the home relay will be operated in the usual manner by alternately removing and throwing on the main battery at the distaut station, in the usual manner of simple telegraphing; but if, in the process of sending a message from the home station the main battery is removed, the local battery will, in the local circuit, replace the effect of the said main battery, and a current from the distant station will be divided, a portion going through the local circuit and the remainder through the relay, and the resistance of the said local circuit is made great enough to cause a sufficient portion of the current from the distant battery to pass through the relay to operate it, as when the said local circuit is broken and the whole of the current of the said distant battery is obliged to pass through the said relay.

This system of duplex telegraphy can be employed at way-stations by the use of a local battery, such as hereinbefore described, and a suitable transmitter, the said way-station employin g the battery at the terminal station with which it is not communicating, the transmitter operating to ground the main line and at the same time close its local circuit, as just described for a terminal station.

The drawing shows the arrangement of the instruments and their connections at two terminal stations, A and B, and a way-station, W, arranged, in this instance, to communicate with the terminal station A.

The main batteries M B and M B are here shown as placed with like poles pp toward the main line L, the other poles, at a, being connected with the earth-plates E E by wires to w. The polespp are also connected by levers l l of the transmitters, preferably arranged as continuity-keys; but they may be common keys, each to open and close a shunt around the main battery, connected with the earth by wires 6, said keys operating to cut off the current of the main batteries from the main line, in the usual manner. The main circuit is thus from the main battery M B, through home relay B, to the main line L, and through the distant relay B, to the distant main battery M B, thecireuit being completed through the earth.

The local batteries L B L B are connected, by the wires c, with the main line at points 01 d, between the main batteries and the relays R It, similar poles p p to those 19 11 of the main batteries being connected to the same electrodes of the said relays. These local circuits, after passing through the relays, are completed by the wires 6 fe f, joining the main line at points g g on the other side of the relay from the points d d, and rheostats Rh Rh are located in the circuit of the said local batteries, by which the electromotive force of the said batteries acting upon the relays m be made equal to that of the main battery. The local circuits contain a closing and breaking point, 2, controlled by the same key or transmitter Z Z that controls the main battery, the points of the said transmitter being so arranged that the said point 2 is closed simultaneously with the removal of the main battery from the line, and is opened when the said main battery is thrown upon the line.

The lever Z may be operated directly by hand, but is preferably operated by a local battery and finger-key, as shown by the diagram, in the well-known manner. tion with the said lever will be readily understood from the drawing, the main battery, as before said, being connected with the lever l, carrying upon it a spring, 7', insulated therefrom at its fixed point 3, where it is connected directly, by the wire i, with the coils of the relay and main line, the said spring 7' resting normally pressed, by its own elasticity, into electrical contact with the lever Z at the point 4, so that when the said transmitter or key is open, as shown at station A, the circuit of main battery passes directly from lever 1 through the said springr to the line, the current of the said battery passing through the said line to the ground at the distant station. When in this position the spring 8, carried by the said lever land insulated therefrom, is separated at 2 from its co-operatin g contact-point t, the said spring 8 and contact-point t forming, as shown,

The electric eonneca portion of the local circuit of the battery L B. When the lever l is depressed or closed the point 5 of the spring 0 comes in contact with its co-operating point a, connected directly with the earth by wire 6, and at the same timethe point 4 of the said spring becomes separated from the lever 1, opening the circuit of the main battery and connecting the main line directly, by spring 1", contact-point u, and wire 6, with the earth, while at the same moment the spring 8 closes with its contact-point it, thus throwing the current of the local battery L B through the coils of the relay R; and since the effect of the batteries M B L B upon the said relay is the same the substitution of one for the other bythe said operation of the transmitter produces no effect upon the said relay. The current of the local battery L B will divide at the points (I g, nearly the whole of it passing directly from d to g through the coils of the relay 1t, and the remainder passing through the line L and distant relay B, but the resistance of the latter circuit is so great with relation .to that through the home relay B that only an exceedingly small portion of the current will pass through the said distant relay, its effect being wholly inappreciable therein.

It will thus be seen that by the operation of the transmitter no effect is produced upon the home relay while the main-battery current is removed from the line and the distant relay thereln causing the said relay to operate.

It being understood that the operation of the transmitter at one station--as, for example, station Aproduces no effect upon the relay R at that station, it remains to be shown in what manner it operates the relay It at the distant station B irrespective of the condition; of the transmitter at the said station.

The main batteries being placed to oppose one another, and both transmitters being open, as the one is shown at station A, the currents of the said batteries will pass to line in-opposite directions and neutralize one another, causing the relays to remain open. If the transmitter at station A be closed, the current of the main battery M B will be removed from the line and the circuit of the local battery L B will be closed, and by this operation a minute friction of the current of the said local battery will be substituted in the distant relay R for the whole current of the main battery M B, so that the efl'ect of the distant battery lVl"B on the said distant relay will no longer be neutralized, and it will be closed by the said current giving its signal in response to the operation of the transmitter at station A, as desired. If, however, the transmitter at station A had been similarly operated when the transmitter at station B was closed, as shown in the drawing, there would be no current from either main battery, and the relay at station B would close under the effect of its local battery L B.

Having thus described the action of the distant relay It, under either condition of its transmitter Z, when the home transmitter l is closed, it remains to show what the effect would be when thehome transmitter lis opened. As before described, if the distant transmitter is also open the distant relay will be opened, owing to the neutralizing effect of the two mainbattery currents; but it the distant relay be closed the main-battery current from the home station on arriving at the point g will divide, a portion passing through the now closed local circuit 0 c and the battery and rheostat therein, while the remainder would pass through the coils R, spring 7", and wire 6, to the ground in the opposite direction to the current of the local battery L B. The resistance of the local circuit, outside of the relay, is made so great, by properly adjusting the rheostat and battery therein, that a sufficient portion of the main current from the distant station may pass through the coils ofthe relay to neutralize the effect of the local battery therein and cause it to give the open signal, as before described, when both the main currents are passin g therethrough.

The comparative strength needed for the main and local batteries may be readily determined by experiment, it being only necessary that'the resistance in the local circuit shall be so great as to cause a sufiicient por tion of the current of the distant main battery to pass through the coils of the relay to operate the same. I have found in practice that, with the main line about two hundred and fifty miles in length, the apparatus works very satisfactorily with the main battery of about double the strength of the local battery, and l have found the effect of the static discharge, and similar. secondary currents, to be wholly inappreciable in lines upward of four hundred miles long, it being probably neutralized by thepeculiar arrangementofcurrents employed. By this method of maintaining the balance or uniform condition of the relay during the operation of the transmitter at the same station therewith, I have found in practice that avery large margin exists, so that a nice or delicate adjustment of the resistance and battery power in the local circuit is not needed, and when it has once been properly adjusted to have about an equal effect with the main battery upon the relay, it will remain in adjustment for a considerable length of time regardless of the changes ,of condition constantly taking place in any long line.

An exact equality between the effect of the main and local battery is not needed in this system as it is in others, so that the matter of adjusting to give good operation is very easily accomplished, and l have found in actual use that with the same main and local batteries and resistance in the localcircuit the relay operated well when connected with main lines widely different in resistance.

It will be seen that a telegraph of this system can be operated at Way as Well as at terminal stations.

A way-station is shown at W, connected to transmit to and receive from station A, it using the main battery at the terminal station B for this purpose. To do this the main line leading toward station B is connected with the lever Z of the transmitter at station W, the remaining connections at the said station being the same as at the transmitting-station B, the corresponding parts being indicated by the same letters with the indexfigure 2 annexed. The transmitter at station B will be kept open, or the whole apparatus at that station will be cut out by a wire leading from the pole p of the main battery M B to the main line L, beyond the point g, while the station W is communicating with station A.

The whole apparatus is then precisely the same as before described, except that the wire a connected with the pole p of the main battery M B is prolonged from station B to station W by the main line. By this method the instruments, with the exception of the key or transmitter, are all the same, or may be all the same, as those of ordinary single-transmission telegraph.

It'desired, the local circuit may pass through a separate coil in the relay, instead of using a single coil placed in both main and local circuits, as shown. In this case the current of the distant station will not divide, as hereinbefore described, at the point g, but will either directly oppose and neutralize the current of the home main batteryin the main-circuit coil or will balance and a-nnul the effect of the current of the local battery.

I claim 1. That improvement in the art of duplex telegraphy which consists in maintaining a relay unaffected by the currents transmitted from the same station therewith for signaling a distant station, as hereinbefore described, by closing an independent local-battery circuit through the said relay when the main-battery current is removed therefrom, and opening the said local circuit when the main-battery current is thrown on, the said local current being equivalent to the main current in its effect on the relay at that station, but having no ap preciable effect on other relays in the main circuit, substantially as and for the purpose described.

2. In a duplex-telegraph system, the main battery and line and relay therein, and alocal battery and circuit passing through the said relay and adjusted to produce an effect upon the said relay substantially equal and of the same character with that of the main battery, combined with a transmitting-instrument provided with closing-points arranged to close the local circuit in the movement by which the main battery at the home station is removed from the line, and open the said local circuit by the movement that puts the main home battery to line,'substantially as and for the purpose described.

3. In a duplex-telegraph system, the main battery and its circuit and relay therein, and the local circuit joining the said main circuit on either side of the said relay, the coils of which are thus common to both the said circuits, and a battery and rheostat in the said local circuit, whereby itsefl'ect on the relay is made substantially the same as that of the main battery, and the impulses from a distant station are confined mainly to the said relay, combined with a suitable circuit-controller to close the said local circuit only when the main battery at the same station is removed from the line, whereby a current from a distant station will produce the same effect upon the said relay whether it is under the additional influence of the current from the main or local battery at its own station, substantially as and for the purpose set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JOHN (JORNELI US WILSON.

Witnesses:

J 0s. P. LIVERMORE, L. F. CONNOR. 

